ZXCD1000
It is well known that this kind of distortion is particularly
unpleasant to the listener. The two scope traces clearly
show the lack of such artifacts with the Zetex solution
Other Solutions - Stereo, Closed Loop and
Higher Powers.
STEREO
It is possible to duplicate the above solution to give a 2
channel stereo solution. However if the oscillator
frequencies are not locked together, a beat can occur
which is acoustically audible. This is undesirable. A
stereo solution which avoids this problem can be
achieved by synchronising the operating frequencies
of both ZXCD1000’s class D controller IC’s, by slaving
one device from the other. This is illustrated in Figure 8.
ZXCD1000
CX1
Audio A
Triangle A
Osc A
Dist
5V5
Out A
9VA
VCC
9VB
Gnd2
Out B
Gnd
RX1
1.5k
MASTER
Cosc
Osc B
ZETEX Class D Solution. (10W into 4Ω)
Note lack of Crossover Artifacts
Triangle B
RX2
1.5k
Audio B
CX2
ZXCD1000
Audio A
Triangle A
5V5
Out A
9VA
VCC
9VB
Gnd2
Out B
Gnd
O/C
Osc A
Dist
Cosc
SLAVE
O/C
Osc B
Triangle B
Audio B
Figure 8.
Frequency sync for Stereo Apps.
Here OscA on the master is used to drive both
TriangleA and TriangleB inputs on the master. OscB on
the master is used to drive both TriangleA and
TriangleB inputs on the slave. In order to achieve the
increased drive capabilty required by the OscA/B
outputs on the master, 1.5kΩ pull down resistors are
added from these pins to ground. The slave oscillator is
disabled by connecting pin 4 (dist) to ground. Great
care must be taken when linking the triangle from the
master to the slave. Any pickup can cause slicing errors
and result in increased distortion. The best connection
method is to run two tracks, side by side, from the
master to the slave. One of these tracks would be the
triangle itself, and the other would be the direct local
ground linking the master pin9 ground to the slave pin
9 ground.
Typical Class D Solution.
Note Large Crossover Artifacts
ISSUE 1 -MARCH 2001
9
ETC [ ETC ]
